The present invention relates to an organic electroluminescence display device (which may be referred to as an organic EL display device), and a method of producing the same.
More specifically, the present invention relates to an organic EL display device having a large luminescence pixel area to be suitable for display devices (displays) for the personal use and industrial use; and a production method making it possible to obtain such an organic EL display device effectively.
Conventionally, there have been suggested EL display devices wherein EL elements, each of which is composed of a luminescent layer sandwiched between electrodes, are driven (are caused to cause luminescence) through scanning electrode lines or signal electrode lines arranged in a matrix form. To make their luminescence pixels highly fine, it is required to prevent a voltage drop and a response delay based on the wiring resistance of the scanning electrode lines and the like.
As shown in FIG. 17, therefore, there is suggested an inorganic EL element comprising first transparent electrodes (lower electrodes) 102, an inorganic luminescent layer 104 and second electrodes (opposed electrodes) 105 which are successively deposited on a glass substrate 101, wherein auxiliary electrodes 103 for resistance-reduction and the first transparent electrodes 102 are electrically networked to each other on the same plane and they are electrically connected to each other in side ends of the first transparent electrodes 102 and non-luminescent portions.
One of EL elements having this type of auxiliary electrode is an EL element disclosed in Japanese Patent Application Laid-Open (JP-A) No. 1996-180974.
As shown in FIG. 18, JP-A No. 1999-31590 suggests an organic EL element wherein metal electrodes 203 are formed, in the vicinity (non-luminescent portions) of transparent electrodes 202 formed in a simple matrix form on a substrate 201, so as to overlap with four sides of the respective transparent electrodes 202 to connect them electrically, and the metal electrodes 203 are covered with an electric insulation layer 206, thereby suppressing the electric resistance of the transparent electrodes 202 by the metal electrodes 203.
On the other hand, as shown in FIG. 19, WO97/34447 discloses an organic EL element comprising a flattening layer 306, lower electrodes 302, an organic luminescent layer 304 and opposed electrodes 305 which are successively deposited on a supporting substrate 301, wherein an auxiliary wiring layer 303 which is electrically connected to the lower ends of the lower electrodes 302 is formed and the auxiliary wiring layer 303 is embedded in the flattening layer 306.
In the EL element shown in FIG. 17, however, the first transparent electrodes (lower electrodes) and the auxiliary electrodes are arranged on the same plane and they are electrically connected to each other in the state that they overlap with each other. Moreover, the luminescent layer is deposited directly on the transparent electrodes and the auxiliary electrodes. For these reasons, many level-differences, which result from the film thicknesses of the transparent electrodes and the auxiliary electrodes, are generated. Therefore, there arises a problem that crosstalk, which is a phenomenon of luminescence of pixels other than selected pixels, is caused by a short circuit between some opposed electrode and some lower electrode, or a problem that display defects, such as generation of a non-luminescence line, which is a phenomenon that light from selected pixels is not emitted by the snapping of the opposed electrode, are easily generated.
Since the transparent electrodes and the auxiliary electrodes are formed on the same plane, the sectional area of the auxiliary electrodes themselves is so small that sufficient measures cannot be taken for making the luminescence pixels highly fine. Particularly in the case that the luminescence pixels are made highly fine to make the electric resistance of the transparent electrodes to, for example, 1 kxcexa9 or more, it is not easy to adjust the electric resistance of the transparent electrodes to a low value, for example, 100xcexa9 or less by changing the width or the thickness of the auxiliary electrodes.
Furthermore, the transparent electrodes and the auxiliary electrodes are formed on the same plane. Therefore, if the transparent electrodes and the auxiliary electrodes are subjected to positional slippage, the transparent electrodes adjacent to the auxiliary electrode subjected to the positional slippage are short-circuited through this auxiliary electrode so that a display defect is generated. Thus, a problem that the yield in production is lowered arises.
In the case of the organic EL element shown in FIG. 18, the problem that the transparent electrodes are short-circuited by the positional slippage of the metal electrodes can be avoided since the metal electrodes are covered with the electric insulation layer. However, the metal electrodes wired on the same plane where the transparent electrodes are wired are formed to overlap with the edge sides of the transparent electrodes. Therefore, the level-differences resulting from the thicknesses or deposition heights of the transparent electrodes and the metal electrodes become more notable so that a short circuit is caused between some transparent electrode and some opposed electrode. Thus, there arises a problem that crosstalk and display defects such as generation of a non-luminescence line is more easily caused than the case of the EL element shown in FIG. 17.
Furthermore, in the case of this organic EL element, the metal electrodes are made, on the same plane where the transparent electrodes are made, so as to connect electrically only to the four sides of the transparent electrodes, which do not produce an effect on the luminescent area of the EL element. However, the transparent electrodes are covered with the metal electrodes. Therefore, if the sectional area of the metal electrodes is made large, a problem that the luminescent area is reduced is caused, resulting in a problem that a luminescent brightness cannot be sufficiently obtained if the luminescence pixels are made highly fine.
On the other hand, in the organic EL display device disclosed in the PCT WO97/3447 publication, the auxiliary wiring layer is embedded in the flattening layer or the like; therefore, the level-differences resulting from the thickness of the auxiliary wiring layer is not generated and the following advantages are produced: the yield in production is high, and crosstalk and display defects such as generation of a non-luminescence line are not caused very much. However, the electrical connection portion between the auxiliary wiring layer and the lower electrode is positioned at the side end of the lower electrode; therefore, it is difficult to make the sectional area of the auxiliary electrode large. If the sectional area is made large, a problem that the area of the luminescence pixels is reduced arises.
Thus, the inventors of the present invention made eager investigations on the above-described problems. As a result, the inventors have found that the problems in the prior art can be solved by wiring a part of the auxiliary wiring layer on a face different from the face on which the lower electrodes are wired and connecting the auxiliary wiring layer electrically in non-luminescent portions in the organic EL display device, or by arranging an electric insulation layer between the lower electrodes and the auxiliary wiring layer and thus connecting the auxiliary wiring layer electrically in non-luminescent portions even if the auxiliary wireing layer and the lower electrodes are wired on the same plane.
That is, an object of the present invention is to provide an organic EL display device which has a luminescence pixel area and a high luminescent brightness, and makes it possible to exclude bad effects, such as generation of display defects based on the thickness of an auxiliary wiring layer, and to make the sectional area of the auxiliary wiring layer large.
Another object of the present invention is to provide a production method making it possible to produce, with a high yield, an organic EL display device which has a large luminescence pixel area and which excludes bad effects, such as generation of display defects based on the thickness of an auxiliary wiring layer.
[1] One aspect (first invention) of the present invention is an organic EL display device having a supporting substrate on which lower electrodes electrically connected to auxiliary wiring layers, an organic luminescent medium, and opposed electrodes are successively disposed, wherein the lower electrodes and the opposed electrodes are disposed in a XY matrix, characterized in that the auxiliary wiring layers and the lower electrodes are wired in different planes, and the auxiliary wiring layers are electrically connected to the lower electrodes in non-luminescent portions of the organic EL display device.
By constituting the device in this way, the electric connecting parts do not overlap with luminescent portions. Therefore, the light quantity taken out from the lower electrode side can be made large so that the value of the luminescent brightness of the organic EL display device can be made large.
Since the auxiliary wiring layers and the lower electrodes are wired in the planes different from each other in the perpendicular direction, flattening can easily be attained so that bad effects, such as generation of a short circuit resulting from the film thickness of the auxiliary wiring layers, can be removed.
Furthermore, since problems of a short circuit between the lower electrodes adjacent to each other or between the lower electrodes and the opposed electrodes are not caused, the thickness or the width of the auxiliary wiring layers can be made so large that the sectional area thereof can be made large. The driving voltage (power consumption) of the organic EL display device can be made small, and crosstalk and display defects such as generation of non-luminescence lines can be reduced.
[2] At the time of constituting the organic EL display device of the first invention, it is preferred that an electric insulation layer is disposed between the auxiliary wiring layers and the lower electrodes.
By constituting the device in this way, the auxiliary wiring layers can be embedded in the electric insulation layer. Therefore, even if the auxiliary wiring layers are disposed, the surface can be flattened. Consequently, electric insulation between the lower electrodes adjacent to each other or between the lower electrodes and the opposed electrodes can be surely kept.
[3] At the time of constituting the organic EL display device of the first invention, it is preferred that the auxiliary wiring layers are electrically connected to the lower electrodes through via holes made in the non-luminescent portions of the organic EL display device.
By constituting the device in this way, the snapping of the lower electrodes, resulting from difference in the thickness of the auxiliary wiring layers, is decreased so that the auxiliary wiring layers can be surely connected electrically to the lower electrodes.
[4] Another aspect (second invention) of the present invention is an organic EL display device having a supporting substrate on which lower electrodes electrically connected to auxiliary wiring layers, an organic luminescent medium, and opposed electrodes are successively disposed, wherein the lower electrodes and the opposed electrodes are disposed in a XY matrix, wherein the auxiliary wiring layers and the lower electrodes are wired in the same plane, the auxiliary wiring layers are electrically connected to the lower electrodes in non-luminescent portions by electric connecting parts provided therein, and an electric insulation layer is disposed between the auxiliary wiring layers and the lower electrodes, except the electric connecting parts.
By constituting the device in this way, the electric connecting portions of the auxiliary wiring layers and the lower electrodes do not overlap with luminescent portions. Therefore, the light quantity taken out from the lower electrode side can be made large so that the value of the luminescent brightness of the organic EL display device can be made large.
Since the electric insulation layer is formed between the lower electrodes and the auxiliary wiring layers, which are wired in the same plane, except the electric connecting parts, the level-differences resulting from the thicknesses of the lower electrodes and the auxiliary wiring layers are cancelled by the electric insulation layer so as not to cause any short-circuit between the opposed electrodes, and the lower electrodes and the auxiliary wiring layers, or the snapping of the opposed electrodes. Consequently, crosstalk and display defects such as generation of non-luminescence lines can be reduced.
[5] At the time of constituting the organic EL display devices of the first and second inventions, it is preferred that the surface of the electric insulation layer is flattened.
By constituting the devices in this way, the thickness of the auxiliary wiring layer causes no trouble so that the yield in production is improved and crosstalk and display defects such as generation of non-luminescence lines can be more reduced.
[6] At the time of constituting the organic EL display devices of the first and second inventions, it is preferred that side surfaces of the via holes for connecting the auxiliary wiring layers and the lower electrodes are made into a forward-tapered form.
By constituting the devices in this way, the snapping of the lower electrodes by the edge of the electric insulation layer is decreased. Thus, the lower electrodes can be surely connected electrically to the auxiliary wiring layers. By constituting the device in this way, in the electric connecting parts of the auxiliary wiring layers and the lower electrodes, the contact area therebetween can be made large because of wide apertures. Thus, the adhesiveness therebetween can be made high. Furthermore, a conductive material or the like can easily be filled into the via holes from their wide apertures. Thus, the production also becomes easy.
[7] At the time of constituting the organic EL display devices of the first and second inventions, it is preferred that the lower electrodes are extended into the via holes for the electrical connection.
For example, if the same conductive material as for the lower electrodes or the auxiliary wiring layers is filled into the via holes and the lower electrodes are extended, the electrical connection between the lower electrodes and the auxiliary wiring layers is made surer.
[8] A further aspect (third invention) of the present invention is a method of producing an organic EL display device having a supporting substrate on which lower electrodes electrically connected to an auxiliary wiring layers, an organic luminescent medium, and opposed electrodes are successively disposed wherein the lower electrodes and the opposed electrodes are disposed in a XY matrix, the method of an organic EL display device comprising the steps of:
wiring the auxiliary wiring layer and the lower electrodes in planes which are partially different; and
connecting the auxiliary wiring layers electrically to the lower electrodes in non-luminescent portions.
By carrying out the invention in this way, the electrically connecting portions of the auxiliary wiring layers and the lower electrodes can easily be disposed in other than the luminescent portions of the organic EL display device. Since the auxiliary wiring layers and the lower electrodes are wired in the planes different from each other in the perpendicular direction, flattening can easily be attained. Moreover, the sectional area of the auxiliary wiring layer can be made large; therefore, driving voltage (power consumption) of the organic EL display device can be made small and further crosstalk and display defects such as generation of non-luminescence lines can be more reduced.
[9] At the time of carrying out the method of producing the organic EL display device of the third invention, it is preferred that the invention comprises the step of disposing an electric insulation layer between the lower electrodes and the auxiliary wiring layers.
By carrying out the invention in this way, the auxiliary wiring layers can be embedded in the electric insulation layer to be made flat, and the electric insulation between the auxiliary wiring layers and the lower electrodes adjacent thereto can be surely kept.
[10] At the time of carrying out the method of producing the organic EL display device of the third invention, it is preferred that the invention comprises the steps of forming via holes in the non-luminescent portions; and connecting the auxiliary wiring layers electrically to the lower electrodes through the via holes.
By carrying out the invention in this way, the snapping of the lower electrodes, resulting from difference in the thickness of the auxiliary wiring layers, is not caused so that the auxiliary wiring layers can be surely connected electrically to the lower electrodes.
[11] A still further aspect (fourth invention) of the present invention is a method of producing an organic EL display device having a supporting substrate on which lower electrodes electrically connected to auxiliary wiring layers, an organic luminescent medium, and opposed electrodes are successively disposed wherein the lower electrodes and the opposed electrodes are disposed in a XY matrix, the method of producing an organic EL display device comprising the steps of:
wiring the auxiliary wiring layers and the lower electrodes in the same plane;
forming electrical connecting parts in non-luminescent portions to connect the auxiliary wiring layers electrically to the lower electrodes; and
disposing an electric insulation layer between the auxiliary wiring layers and the lower electrodes, except the electrical connecting parts.
By carrying out the invention in this way, the electrical connecting parts of the auxiliary wiring layers and the lower electrodes can easily be disposed in other than the luminescent portions. Since the electric insulation layer is disposed between the lower electrodes and the auxiliary wiring layer, the electric insulation between the auxiliary wiring layers and the opposed electrodes can be surely kept even if the auxiliary wiring layers and the lower electrodes are wired in the same plane. By carrying out the invention in this way, the level-differences resulting from the thicknesses of the lower electrodes and the auxiliary wiring layers are cancelled by the electric insulation layer, so as to attain flattening. Therefore, the sectional area of the auxiliary wiring layers can also be made large, so that crosstalk and display defects such as generation of non-luminescence lines can be reduced.
[12] At the time of carrying out the methods of producing the organic EL display device of the third and fourth inventions, it is preferred that the inventions comprise the step of flattening the surface of the electric insulation layer.
By carrying out the inventions in this way, the thickness of the auxiliary wiring layers causes no trouble so that the yield in production is improved and crosstalk and display defects such as generation of non-luminescence lines can be more reduced.
[13] At the time of carrying out the methods of producing the organic EL display device of the third and fourth inventions, it is preferred that the inventions comprise the step of making a side surface of the via holes into a forward-tapered form.
By carrying out the inventions in this way, the snapping of the lower electrodes by the edge of the electric insulation layer is more reduced. Moreover, by carrying out the inventions in this way, vacuum deposition or the like is used to fill a conductive material easily into the via holes.
[14] At the time of carrying out the methods of producing the organic EL display device of the third and fourth inventions, it is preferred that the inventions comprise the step of extending the lower electrodes into the via holes to connect the lower electrodes electrically to the auxiliary wiring layers.
For example, if the same conductive material as for the lower electrodes or the auxiliary wiring layers is filled into the via holes to extend the lower electrodes, the snapping of the lower electrodes is more decreased so that electrical connection between the lower electrodes and the auxiliary wiring layers is made surer. As a result, the yield in production can be improved.